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Date: Tue, 06 Nov 2007 11:42:31 +0000
From: Christopher Key <cjk32@cam.ac.uk>
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To: Achilleas Mantzios <achill@matrix.gatewaynet.com>
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Cc: freebsd-hardware@freebsd.org
Subject: Re: Implementing a "normally open" relay
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Achilleas Mantzios wrote:
> Hi,
> i am building a home security system based on zoneminder under FreeBSD 6.2.
> I think i have it all sorted out, except a way to drive an external alarm upon
> camera motion.
>
>   

> Have two states:
>
> a) (normal) Have the two wires isolated from eachother, ground, voltage
> b) (alarm) Connect the wires together (shortcircuiting the EOL).
>
> Could it be done someway with /dev/cuad* /dev/lpt*
>
>
>   
Probably overkill, but you can buy general purpose relay boards driven 
from the parallel port, e.g.,

http://www.electronic-kits-and-projects.com/3074.htm

Chris